#! /usr/bin/env sh

set -e

tmpHomePath="$(mktemp -d "${TMPDIR:-/tmp}/nix-prefetch-url-XXXXXXXXXX")"
cleanup() {
    chmod -R u+w "$tmpHomePath"
    rm -rf "$tmpHomePath"
}
trap cleanup EXIT

info() {
    echo "$1" 1>&2
}

# Returns a name based on the url and reference
#
# This function needs to be in sync with nix's fetchgit implementation
# of urlToName() to re-use the same nix store paths.
url_to_name() {
    url=$1

    basename "$url" .git | cut -d: -f2
}

get_sha256() {
    url="$1"
    storePathName="$(url_to_name "$url")"
    hashType="sha256"

    tmpOut="$tmpHomePath/$storePathName"
    info "Prefetching '$url'..."

    curl --follow "$url" >"$tmpOut"

    # Compute the hash.
    hash=$(nix-hash --flat --type "$hashType" --sri "$tmpOut")

    # Add the downloaded file to the Nix store.
    finalPath=$(nix-store --add-fixed "$hashType" "$tmpOut")

    info "  -> Downloaded to '$finalPath'"
    echo "$hash"
}

old_version="$(jq .version --raw-output <./files.json)"
new_version="$(curl --follow https://download.tails.net/tails/stable/ 2>/dev/null | html2text -links | grep --regexp='\s*[0-9]\. tails-amd64-' | sed 's/\s*[0-9]\. tails-amd64-\(.*\)\//\1/')"

if [ "$old_version" = "$new_version" ]; then
    # No need to update.
    info exit 0
fi

final_version="amd64-$new_version"

cat <<EOF | jq . | tee ./files.json
{
    "version": "$new_version",
    "files": {
        "iso.sig": "$(get_sha256 "https://tails.net/torrents/files/tails-$final_version.iso.sig")",
        "iso": "$(get_sha256 "https://download.tails.net/tails/stable/tails-$final_version/tails-$final_version.iso")"
    }
}
EOF

# vim: ft=sh